1. Field of the Invention
The present invention relates generally to a capacity control valve for variably modulating the capacity or pressure of a process fluid. More particularly, the invention relates to a capacity control valve which modulates the capacity or pressure in a control chamber of an air-conditioning system in a quick manner.
2. Description of the Related Art
There have been known as a relative art of the present invention capacity control valves for a variable displacement type swash plate compressor in an air-conditioning system. The relative art of the capacity control valve is illustrated in FIG. 15.
In FIG. 15, a pressure sensing element 210 is disposed in a suction chamber 206 which is located at the lower end of a capacity control valve 200. The pressure sensing element 210 is formed by a resilient bellows with a biasing spring which is disposed inside the bellows and the element is constructed in such a way that the upper end of the element moves by a contraction due to a suction pressure Ps supplied from an external. At the upper end of the pressure sensing element 210, an intermediate rod 207 is disposed in a guide passage of a housing 220 in an axially movable manner. Furthermore, a valve body 201 connected to the intermediate rod 207 is disposed in a valve hole 208, as shown in FIG. 15, at the upper portion of the housing 220. Opening or closing motion of the valve body 201 corresponds to a separation or contact, respectively, of the valve body with the valve seat of the valve hole 208, and hence an opening or closing of the valve hole 208, respectively.
The housing 220 constitutes Ps supply port, Pd discharge port, and Pc crank chamber supply port wherein the Pd discharge port is connected to the valve hole 208 by means of a through communication passage 209. When the valve hole 208 opens, the valve hole 208 is directly connected to the Pc crank chamber supply port and a process fluid is allowed to a crank chamber which is not shown in FIG. 15.
Opening or closing of the valve body 201 is modulated by changing the set supply pressure (Ps set value) of the pressure sensing element 210 in accordance with the generated force of an electromagnetic solenoid coil device 202 which is disposed in the upper end portion of the capacity control valve 200, and a capacity control of the variable displacement compressor is achieved by modulating the crank pressure Pc of the crank chamber while controlling the flow under the discharge pressure Pd guided to the crank chamber of the variable displacement compressor in accordance with an opening degree of the valve body 201.
The pressure sensing element 210 disposed in the suction chamber 206 has a load characteristic such that the element expands or contracts in accordance with the suction pressure Ps within the normal use range of the suction pressure Ps.
When no electric current is supplied to the electromagnetic solenoid coil device 202, the valve body 201 is maintained at a fully open position by the urging spring force of a return spring 203. This fully opened position corresponds to a fully unloaded state. When the current is supplied to the solenoid coil device 202, an electromagnetic attractive force is generated between a plunger 40 and a fixed iron core 205. The valve body 201 maintains its fully opened position, namely an insensitive zone, until the electromagnetic force becomes larger than the opposing urging force of the return spring 203.
However, when the electromagnetic force becomes larger than the urging force of the return spring 203, the valve body 2011 moves in a direction closing the valve, entering Ps control range in which the more the coil current supply, the larger the valve closing force, and the lower the Ps set value.
In this type of capacity control valve 200, it is difficult to reduce a cooling load because, in case of a great cooling load, the valve quickly closes due to the suction pressure Ps. Consequently, the compressor has to be stopped by means of clutch and the air-conditioning system needs to be turned off.
Diameter of the connected rod varies in place, and when the pressure areas of the rod are subjected to the suction pressure Ps, discharge pressure Pd, or crank chamber supply pressure Pc, the balance of the forces acting on the operation mechanism of the rods including the valve body (according to the ratio of the pressure receiving area of the respective rod diameters) causes substantially a bad influence on the valve opening degree of the valve body 201.
Furthermore, a variation in the crank pressure Pc due to the different operation modes of a compressor may cause uncontrollable disturbances to the suction pressure Pc. Therefore, an accurate current control to the electromagnetic solenoid coil does not help improve the capacity control precision of the valve according to a preset suction pressure Ps.
A connection rod between the pressure sensing element 210 and the fixed iron core 205 comprises an intermediate rod 207, a valve body rod 201A, and a plunger rod 204A. In the connection rod, a wear of the joint portion of each rod causes a serious problem of the valve opening degree of the valve body 202.
Performance of the connection rod between the pressure sensing element 210 and the valve body 201 is worsened with respect to the opening degree of the valve body 201 because a wear of the contact surface causes the total length of the connection rod to be shortened since each joint is formed by a simple contact of the two adjacent rods.
This type of capacity control valve for variable displacement compressors suffers from the following problems due to the above mentioned arrangements. Primarily, the capacity control valve does not allow a quick change in the pressure of the control chamber. Therefore, such a variable displacement compressor, for instance, will require a clutch, which may result in a cost increase due to the more complicated structure of the variable displacement compressor.
Since no consideration is given in terms of the force balance which is affected by the pressure areas of the valve body, valve body rod, intermediate rod, and so on, to each of which the process fluid exerts a corresponding pressure, it is hard to maintain the control accuracy of the capacity or pressure of the process fluid under the control pressure.
Furthermore, the valve operation in which the valve body, valve body rod, intermediate rod and so on, are individually connected may cause a decrease in accuracy of the valve opening or closing action due to wears of the joint portions.
The present invention is introduced to resolve the above mentioned problems. A primary technical goal which this invention tries to achieve is to realize an accurate control of the pressure or the capacity of the capacity control valve without being affected by other pressures, and to be able to modify the pressure or the capacity of the capacity control valve as soon as an operation load exceeds a predetermined value. For example, when a clutch is needed for a variable displacement compressor, this invention eliminates such a clutch from the compressor and reduces the extra cost to install a clutch in the variable displacement compressor.
Another goal is to obtain a capacity control valve wherein the force balance acting on the operation mechanism of the connection rod including the valve body is arbitrarily chosen and the capacity or the pressure in the control chamber is accurately controlled based on a predetermined suction pressure (Pset) without being affected by other pressures.
For example, when the capacity control valve is used in a variable displacement compressor which is controlled by the suction pressure Ps, this invention enables the compressor to implement an accurate control with the predetermined suction pressure (Ps) without being affected by the crank chamber pressure (Pc) or the discharge pressure (Pd).
A further goal is to increase a manufacturing precision and to reduce a production cost by constructing one integral piece of a pressure sensing rod.
Yet another goal is to simplify the assembly process of the pressure sensing rod, the pressure sensing device and the valve housing, and also to improve the operation of the pressure sensing rod wherein the pressure sensing rod and the pressure sensing device are connected before being assembled with the valve housing.
A primary object of the present invention is to resolve the above mentioned technical problems, and a solution to such problems is embodied as follows.
A preferred embodiment of a capacity control valve constructed in accordance with the principles of the present invention is a capacity control valve for controlling the opening area of a valve portion for modulating the capacity or pressure within a control chamber by means of a control pressure fluid, the capacity control valve comprising a capacity chamber, a valve chamber, an action chamber, an action face, a valve body, a valve opening joint portion, an engagement portion, a pressure sensing device and a solenoid portion, the capacity chamber being located in the valve portion and connected with a second communication passage, the valve chamber having a valve seat for a valve hole connected with the capacity chamber and connected with a first communication passage, the operation chamber being connected with the valve chamber and also connected with a detection communication passage, the action face being disposed inside the action chamber and having a pressure receiving area which receives a suction pressure via the detection communication passage, the valve body being integral with the action face and located in the valve chamber in a freely movable manner and having a valve surface which can be freely attached to or detached from the valve seat, the valve opening joint portion being integral with the valve body and having a pressure receiving surface, the engagement portion making a contact with the pressure surface of the valve opening joint portion and being disengaged from the pressure receiving surface when the valve body opens, the pressure sensing device retaining the engagement portion, being located inside the capacity chamber and urging the valve body to open by receiving the process fluid pressure within the capacity chamber, the solenoid portion driving a plunger which has a solenoid rod connected with the valve body in an opening or closing direction of the valve body.
The most preferred embodiment of the present invention is a capacity control valve with an ability of rapidly changing the pressure of a control chamber when a suction pressure Ps is used to modulate a control pressure. For example, there is a necessary case wherein a solenoid current needs to be shut off so as to change a set value during the operation. A capacity control valve in accordance with the present invention is capable of dealing with this kind of situation. More specifically, while the valve is in action, the valve body not only can achieve an accurate capacity control or pressure control by means of Ps under a normal operation, but also, in case of an increased fluid pressure load to be controlled, can quickly open the valve by disengaging the valve opening joint portion from the engagement portion which is connected to the solenoid portion according to commands supplied from the external.
The valve opening joint portion is located between the pressure sensing device and the valve body and, when the valve body is in operation, the valve opening degree is determine by the contact of the valve opening joint portion and the engagement portion according to the force balance among the force given by the solenoid coil according to the current supplied to the solenoid, the force given by the pressure sensing device acted on by the process fluid pressure, and the forces acted on respective faces of the valve body. Under this circumstance, the engagement portion and the valve opening joint portion act together while the sliding surfaces of the engagement portion and the valve opening joint portion maintain a contact. The contact surfaces of the engagement portion and the valve opening joint portion located in the capacity chamber merely form a slidable contact when the valve body quickly opens based on the command given to the solenoid portion by a computer controller which is not shown in the figure, and therefore a relative movement of the valve opening joint portion in a direction opening the valve can be easily transmitted by the engagement portion. As a consequence, a quick opening of the valve body induces the controlled process fluid to quickly discharge to the control chamber, and thus a modulation of the capacityw or pressure value within the control chamber to a desired value will be made possible.